1. Field of the Invention
This invention relates generally to fluid flow control systems, and to mechanical failsafes or shut-off devices for preventing the flow of fluids (eg, gas or liquid streams) upon breakage or failure of components in the system, such as filters or other components. More particularly, the invention relates to devices for preventing the flow-of high-temperature (e.g., up to 1800xc2x0 F.) gas streams upon filter damage.
2. Description of Background Art
Industrial systems in which fluids flow (such as gas turbine power plants, liquid fuel processing plants, hydraulic systems, pneumatic systems, gas treatment or gas processing plants for, e.g. cleaning or reforming fuel gases, oil or gas pipelines, and the like), and in which gases are, e.g. transported, cleansed of entrained particulate matter or treated prior to coming into contact with system components that are susceptible to such particulate matter, often provide treatment systems for removing impurities and/or restricting flow to system design levels. To prevent damage to system components and/or the environment, such systems often are provided with flow limiting or shut-off valve mechanisms. Upon the occurrence of damage, breakage or removal of filter components, these shut-off mechanisms stop the flow of fluid through the system.
In particular, high temperature and high-pressure barrier filter systems are critical to the successful commercialization of PFBC and IGCC coal-based power plant systems. Presently the most commercially ready barrier filter systems are based on candle filter technology. These barrier filter systems generally employ a large number of individual, porous candle filter elements in parallel. Over the past decade, a variety of filter designs based on porous ceramic filter elements have been developed to provide cleanup of particulate-laden flue gas at high temperatures and high pressures (HTHP).
The most common filter design has been based on multiple rigid, cylindrical ceramic filter tubes placed in parallel across the process stream (so-called xe2x80x98candle filtersxe2x80x99). The process conditions to which these filter designs have been exposed have taxed the capabilities of the ceramic materials used to construct the individual filter elements, resulting in periodic failures of a significant proportion of these filter elements. Because the components downstream of these HTHP filters can be extremely sensitive to even small amounts of entrained particulate matter, these failures have revealed the need for a means to ensure the cleanliness of the flue gas downstream of the filter in the case of catastrophic failure of some portion of the filter components. Consequently, the requirements of any system or safeguard device (SGD) designed to deal with these failures must be quite stringent.
Pilot-scale candle filter-based systems have been shown to remove particulate matter down to a concentration of less than 1 ppm (part per million) when in good operating condition. However, in the event of the failure of even a single filter element, the filter system outlet dust loading will increase and thereby potentially damage gas turbine blades, contaminate other downstream processes, and limit the availability of the power system. A filter failure safeguard device which would prevent the flow of particle-laden gas through the failed filter element location would serve to minimize the potential damage to downstream equipment, minimize dust emissions, and allow the power plant to continue operation until a convenient or scheduled outage can be implemented.
Various types of flow limiting/shut-off mechanisms are known in the prior art, see e.g., U.S. Pat. Nos. 5,242,58; 3,261,146; 2,892,512; 2,833,117; 2,687,745; 2,680,451; 2,635,629; 1,983,791. Such mechanisms are characterized by their complicated structure, large number of moving parts, difficulty in installation, limited operational temperature ranges, and/or dependence on entrained particle concentration for activation of the shut-off feature.
There remains a need in the art for improvement to the structure of mechanical fluid flow shut-off devices.
The present invention provides an improvement to the prior art, by providing according to one embodiment a full-flow failsafe, including a reaction tube for containing a flowing fluid stream, a first shell having first apertures at each end thereof for enabling the fluid stream to flow therethrough, a first one of the first apertures being coupled to the reaction tube, a first sealing plug movably positioned within the first shell, the first sealing plug being oriented in a first position during normal operation of the reaction tube to permit fluid flow through the first shell, and being moved by increased fluid velocity to a second position wherein the first sealing plug forms a sealing contact with a second one of the first apertures, upon failure or breakage of the reaction tube, and at least one first locking mechanism supporting the first sealing plug in the first position, and being moved to a locking position for securing the first sealing plug in the second position in response to the movement of the sealing plug.